But the doctors say it's too soon to say how long the treatment will take and what lasting damage the 53-year-old might have from three slipped discs she suffered while in prison.

Tymoshenko arrived in the German capital on Friday night and immediately checked into the Charite, one of Europe's largest hospitals, where doctors performed scans on her back.

"We can't say how long she will have to stay here. That depends on what therapeutic path is taken," said Dr Karl Max Einhaeupl, the hospital's chief executive, who visited Tymoshenko during her two and a half years in jail on charges of abuse of office.

She was released two weeks ago after the ouster of pro-Russian President Viktor Yanukovych.

Einhaeupl said doctors would perform more tests and decide by Monday whether to recommend an operation.

Until then, she is receiving medication and doing physical rehabilitation exercises.

If Tymoshenko does have an operation - a routine procedure that can be done in under an hour - the recovery would typically last about four days followed by rehabilitation over several weeks, he said.

Tymoshenko refused to receive invasive medical treatment while in prison, fearing that political opponents might seek to injure her further.

One common treatment for her condition, known as infiltration, involves injecting painkillers and anti-inflammatory drugs into the site of the slipped disc.

The limited treatment that Tymoshenko did receive in prison to relieve pain and prevent her condition from worsening appears to have improved the first slipped disc, which she suffered in October 2011, Einhaeupl said.

In her public appearances in recent days Tymoshenko looked much better than she did immediately after her release, when she appeared on a stage in central Kiev in a wheelchair looking pale and worn out.